Detecting faulty collection of vibration data

Abstract

Vibration data indicative of the health of a machine is collected using a vibration sensor connected to a vibration data collector. After the vibration sensor has been attached to a measurement point on the machine, vibration data is collected that includes a bin of data having a begin time and an end time, and the vibration data is stored in memory of the vibration data collector. First and second average amplitudes of the bin of vibration data collected during first and second time windows in the measurement time period are determined. The slope of the vibration data is calculated based on the ratio of the amplitude difference between the first and second average amplitudes and the time difference between the first and second time windows. The vibration data is either retained in the memory or discarded based on the comparison of the slope to a threshold level.

What is claimed is: 
     
       1. A method for collecting vibration data indicative of health of a machine, the method comprising:
 (a) attaching a vibration sensor to a measurement point on the machine; 
 (b) collecting vibration data including a bin of vibration data that extends over a measurement time period having a begin time and an end time; 
 (c) storing the vibration data in memory; 
 (d) determining a first average amplitude of a first portion of the bin of vibration data collected during a first time window that includes the begin time of the measurement time period; 
 (e) determining a second average amplitude of a second portion of the bin of vibration data collected during a second time window that includes the end time of the measurement time period; 
 (f) determining a slope of the vibration data based on a ratio of an amplitude difference between the first and second average amplitudes and a time difference between a first time in the first time window and a second time in the second time window; and 
 (g) retaining or discarding the bin of vibration data collected in step (b) based on comparison of the slope to one or more threshold levels. 
 
     
     
       2. The method of  claim 1  wherein step (g) comprises deleting the vibration data collected in step (b) from the memory if the slope is greater than a first threshold level. 
     
     
       3. The method of  claim 2  further comprising repeating steps (b) through (g) until the slope is less than the first threshold level, and retaining the vibration data collected in step (b) in memory. 
     
     
       4. The method of  claim 1  wherein step (g) comprises:
 (g1) prompting an operator to choose to retain or discard the vibration data collected in step (b) if the slope is less than a first threshold level and greater than a second threshold level, wherein the second threshold level is less than the first threshold level; and 
 (g2) retaining or discarding the vibration data collected in step (b) based on the choice of the operator. 
 
     
     
       5. The method of  claim 4  wherein the prompting is accomplished with a visual prompt on a display screen. 
     
     
       6. The method of  claim 1  wherein the first time window begins at the begin time of the measurement time period and the second time window ends at the end time of the measurement time period. 
     
     
       7. The method of  claim 1  wherein the first time in the first time window is a mean time of the first time window and the second time in the second time window is a mean time of the second time window. 
     
     
       8. The method of  claim 1  wherein a width of the first time window is no greater than one half of the measurement time period, and a width of the second time window is no greater than one half of the measurement time period. 
     
     
       9. The method of  claim 1  wherein step (c) comprises storing the vibration data in memory of a vibration data collector or memory of an on-line vibration data collection system. 
     
     
       10. A vibration data collector for collecting vibration data indicative of health of a machine, comprising:
 a vibration sensor operable to be attached to a measurement point on the machine and generate a bin of vibration data based on vibration of the machine at the measurement point during a measurement time period having a begin time and an end time; 
 an analog-to-digital converter for converting the vibration signals to digital vibration data; 
 memory for storing the vibration data; 
 a processing device for operating on the vibration data based on execution of commands that:
 determine a first average amplitude of a first portion of the bin of vibration data collected during a first time window that includes the begin time of the measurement time period; 
 determine a second average amplitude of a second portion of the bin of vibration data collected during a second time window that includes the end time of the measurement time period; 
 determine a slope of the vibration data based on a ratio of an amplitude difference between the first and second average amplitudes and a time difference between a mean time of the first time window and a mean time of the second time window; and 
 retain the vibration data in the memory or delete the vibration data from the memory based on comparison of the slope to one or more threshold levels. 
 
 
     
     
       11. The vibration data collector of  claim 10  wherein the analog-to-digital converter, the memory and the processing device are components of a portable handheld measurement device or of an on-line measurement system. 
     
     
       12. The vibration data collector of  claim 10  wherein execution of commands by the processing device causes deletion of the vibration data from the memory if the slope is greater than a first threshold level. 
     
     
       13. The vibration data collector  claim 12  wherein execution of commands by the processing device causes collection of vibration data to continue at the measurement point until the slope is less than the first threshold level, at which point the collected vibration data is retained in the memory. 
     
     
       14. The vibration data collector of  claim 10  wherein execution of commands by the processing device:
 generates a message on a display screen that prompts a user of the vibration data collector to choose to retain or discard the vibration data if the slope is less than a first threshold level and greater than a second threshold level, wherein the second threshold level is less than the first threshold level; and 
 causes the vibration data to be retained in the memory or deleted from the memory based on the choice of the user.